The proposed research will continue an analysis of the properties of the system of cerebral neurons responsive to genital stimulation (genital sensory neurons) in the female cat, and extend the investigation to include the female squirrel monkey. Through the use of chronic single-unit recording methods, the activity of brainstem and diencephalic genital sensory neurons will be examined during the elicitation of behavioral responses by vaginal stimulation in ovariectomized, anestrous and estrogen-treated cats. The objective is an identification of differences in the activity of these neurons in the estrous and anestrous conditions, and an elucidation of some of the neuronal processes controlling receptivity to genital stimuli in the cat. In acute experiments on estrous and anestrous cats, the activity of lateral medullary neurons will be reocrded during genital stimulation in order to elucidate the neuroendocrine control of the estrous cry response. Quantitative analysis of single unit activity and assessment of its relationship to behavioral events will be conducted. Genital sensory mechanisms in the female monkey will be investigated in a series of acute experiments in which the brainstem and subcortical regions of the forebrain are mapped for single-unit responses to vaginal stimulation. The work on the monkey will provide a delineation of the basic organization and sensory properties of cerebral genital sensory neurons in this species. Collectively the findings from studies on the cat and monkey should contribute to an understanding of the mechanisms through which genital sensations influence the expression of mating behavior and the mode of action of gonadal hormones on genital sensory processes.